What does the zeroth law of thermodynamics allow us to define?
2 answers:
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1) By looking at the table of the visible spectrum, we see that blue light has a wavelength in the range [450-490 nm], while red light has wavelength in the range [620-750 nm]. Therefore, red light has longer wavelength than blue light.
2) The frequency f of an electromagnetic wave is related to its wavelength
by the formula
where c is the speed of light. We see that the frequency is inversely proportional to the wavelength, so the shorter the wavelength, the greater the frequency. In this case, blue light has shorter wavelength than red light, so blue light has greater frequency than red light.
3) The energy of the photons of an electromagnetic wave is given by
where h is the Planck constant and f is the frequency. We see that the energy is directly proportional to the frequency, so the greater the frequency, the greater the energy. In this problem, blue light has greater frequency than red light, so blue light has also greater energy than red light.
2) The frequency f of an electromagnetic wave is related to its wavelength
where c is the speed of light. We see that the frequency is inversely proportional to the wavelength, so the shorter the wavelength, the greater the frequency. In this case, blue light has shorter wavelength than red light, so blue light has greater frequency than red light.
3) The energy of the photons of an electromagnetic wave is given by
where h is the Planck constant and f is the frequency. We see that the energy is directly proportional to the frequency, so the greater the frequency, the greater the energy. In this problem, blue light has greater frequency than red light, so blue light has also greater energy than red light.
Missing question in the text of the exercise. Found on internet:
"What is the acceleration due to gravity on the surface of the planet?"
Solution:
The gravitational acceleration at Earth's surface is given by:
where
G is the gravitational constant
M is the Earth's mass
r is the Earth's radius
The Earth's mass can be rewritten also as the product between the Earth's density,
, and its volume (the volume of a sphere of radius r):
Now let's call M' the mass of the new planet, r' its radius and d' its density. The acceleration due to gravity on the surface of the new planet is
(1)
so we need to find M' and r'.
The problem says the radius of the new planet is twice the Earth's radius:
(2)
and that its density is 2/3 of Earth's density:
so the mass M' of the new planet is, with respect to the Earth's mass:
(3)
And if we substitute (2) and (3) into (1), we find the gravitational acceleration on the surface of the new planet:
And since
, we find
"What is the acceleration due to gravity on the surface of the planet?"
Solution:
The gravitational acceleration at Earth's surface is given by:
where
G is the gravitational constant
M is the Earth's mass
r is the Earth's radius
The Earth's mass can be rewritten also as the product between the Earth's density,
Now let's call M' the mass of the new planet, r' its radius and d' its density. The acceleration due to gravity on the surface of the new planet is
so we need to find M' and r'.
The problem says the radius of the new planet is twice the Earth's radius:
and that its density is 2/3 of Earth's density:
so the mass M' of the new planet is, with respect to the Earth's mass:
And if we substitute (2) and (3) into (1), we find the gravitational acceleration on the surface of the new planet:
And since